The use of beta gauge systems to control material treaters is disclosed and claimed in U.S. Pat. No. 3,596,071, hereby incorporated herein by reference. The procedure disclosed therein employs three beta gauges which continuously scan across the material web being treated. The patentee uses conventional feedback control techniques which with the advent of high speed treaters is an inadequate method of control because of the large volume of product lost between the time the apparatus is discovered to be producing an inferior product and the time when adjustments can be made in order to correct the error and put the product back within specification limits.
With the increasing use of digital computers for process control purposes, the analog system of the above patent is outmoded. High speed, flexible usage digital computers now permit rapid action control schemes to be employed. With the older computer systems, control actions are possible only about every 60 seconds and since many of these treaters run at 500-1,000 feet per minute, it can be readily appreciated that considerable amounts of out of limits material can be produced before corrective action can be taken.